#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int a = 0;
	int sum = 0;
	int i = 0;
	while (i<5)
	{
		scanf("%d", &a);
		sum += a;
		i++;
	}
	float b;
	b = sum / 5.0;
	printf("%.1f\n", b);
	return 0;
}